A conventional dome type camera comprises a hemispheric dome cover, and a lens provided inside the dome cover rotatably in tilt and pan directions. They are placed so that the center of rotation of the lens is on the optical axis and corresponds to the center of the dome cover, and this placement provides good images. Such a dome type camera is disclosed, for example, in Japanese published patent application No. 2000-155366 (abstract and FIG. 4).
However, the conventional dome type camera produces vignetting and cannot obtain good images when shooting in the direction of a depression angle.
By the way, the direction of a depression angle is a downward direction with reference to the horizontal direction, provided that the zenith direction of the dome is the upward direction. Accordingly, for example, if a dome type surveillance camera is installed with the dome facing upward, the direction of a depression angle is a downward direction with reference to the horizontal. If the camera is installed on a wall with the dome facing sideways, the direction of a depression angle is a direction toward the wall with reference to the downward direction. Incidentally, vignetting refers to a partial darkening of an image due to a camera case being in part of a shooting area.
As mentioned above, the conventional camera produces vignetting when shooting in the direction of a depression angle. Consequently, for example, it has not been easy to respond to the need to shoot around the place where the camera is mounted and to obtain good images therefrom.